1. Technical Field
The present invention relates to a wide-meshed grid fabric in which the clearance of the meshes is delimited by warp thread bundles composed of multiple warp threads and by weft thread bundles composed of multiple weft threads, the warp threads and the weft threads being interwoven at the points of intersection of the warp thread bundles and the weft thread bundles running at right angles to one another.
The rectangular or square lattice openings formed by the warp thread bundle and the weft thread bundle are referred to in this description as “mesh.”
2. Description of the Related Art
Grid fabrics of this type which, if they are impregnated or coated with a synthetic polymer, are used in particular for reinforcing bitumen-bonded road surfaces or for reinforcing cement-or gypsum-bonded mortar layers, or as geogrids for reinforcing soils, are known from DE 20 00 937; 3120 661; 3136 026; 4123 055, and 199 62 441.
The warp threads and the weft threads are preferably made of high tensile-strength multifilament synthetic yarns, in particular of aramid fiber, polyester, or the like. Glass filament yarns may also be used.
The warp thread bundles and the weft thread bundles are composed of at least four threads.
The compound which encloses the warp thread bundles, the weft thread bundles, and their points of intersection, thus fixing the grid fabric and protecting it against chemical and mechanical stress, may be, depending on the application, a PVC paste, a latex dispersion, or dispersions of bitumen, acrylics, or similar soft plastics, as well as mixtures thereof.
The term “grid fabric” also relates to scrims in which the warp threads and the weft threads are not interwoven at the points of intersection, but are bonded to one another using other techniques, Raschel technology in particular, or also by gluing or welding. Thus, it is desirable to create a grid fabric in which the grid fabric is provided with a larger volume using weaving technology and, if used as a geogrid, to achieve improved interlocking with the soil to be reinforced.
According to one embodiment of the present invention, individual threads of a bundle of threads are longer per mesh than the mesh clearance and are longer than other threads of the same bundle of threads, the longer threads running in a wave pattern and forming at least one open loop or bulge per mesh.
Due to the fact that one portion of the weft or warp threads within the mesh clearance is longer than a second portion of the weft or warp threads of the same bundle of threads, the longer threads form bulges or open loops per mesh which protrude mostly upward or downward from the plane of the grid fabric.
To prevent the bulges or open loops protruding from the plane of the grid fabric from falling back onto the plane of the grid fabric, the grid fabric is stiffened by impregnation or by coating using a synthetic polymer material.
The different lengths of the warp threads and weft threads per mesh may be obtained by using warp threads and weft threads which shrink or expand differently for example under heat treatment.
In scrims, individual warp threads of a warp thread bundle and/or individual weft threads of a weft thread bundle per mesh may be lifted from the grid plane before the scrim passes the point at which the warp threads and weft threads are bonded by gluing, welding, or by using Raschel technology.
Grid fabrics according to DE 199 62 441 A1 are particularly advantageous for use in geotextiles. In this grid fabric, the warp thread bundles are divided into a first warp thread group and a second warp thread group, the first warp thread group intersecting with the second warp thread group of the same warp thread bundle once per mesh in a half-twist. The first warp thread group is always positioned on top and the second warp thread group always beneath it. At the points of intersection of warp threads and weft threads, the threads are interwoven with one another either individually or in groups.
A higher tensile stress in the warp direction results in the threads of the two warp thread groups of a bundle, which run in a zigzag pattern and intersect with each other once per mesh, moving closer together in the area of the points of intersection which in turn results in the grid fabric being less elastic in the warp direction and being able to absorb greater forces without further expansion, and also in a portion of the weft threads looping around the warp thread groups, which are displaced closer to each other, in an S pattern, while the portion of the weft threads interwoven in the opposite phase passes the point of intersection essentially straight, so that this portion of the weft threads is longer per mesh than the portion of the shorter threads which determines the clearance of the meshes.
The grid fabric according to the present invention having loops protruding from the plane of the lattice is particularly advantageous for numerous applications. Not only is improved interlocking with the soil to be reinforced achieved, but the grid fabric according to the present invention is also advantageous for reinforcing hardening compounds and products, e.g., floor pavements, as well as gypsum and concrete products, or as a supporting web in the manufacture of setting or hardening products made of plastic, gypsum or concrete mortar, which are sprayed or formed onto the supporting web so that the loops protrude into the hardened products which remain connected via the supporting web. Furthermore, the grid mat provided with protruding loops is well suited to form the supporting part of a drainage mat. Parts such as, for example, fascines may be attached to or parts such as, for example, steel reinforcements, or drainage tubes, may be inserted through the loops protruding from the plane of the fabric upward, downward or upward and downward.
Finally, the grid fabric according to the present invention is well suited for erosion protection, as an anti-slip mat, or as a snow brake.
The grid fabric having protruding loops and being surrounded with an elastic plastic layer has very high static friction. As an intermediate layer between stacked stone blocks of a retaining wall, this lattice anchored in the embankment may connect the wall to the embankment.